Black Glue Peril

[Phil Allison]

** Hi to all,

the dreaded " Yellow Glue" problem has been mentioned here a few times.

I have exactly the same problem, but the glue is now black instead - with a
KRK 'Rokit 5" powered monitor - from China of course. Both PCBs are
liberally covered in the stuff, more on the amplifier and PSU one.

Symptoms in my example were loud crackling and low volume - which
recovered when I wound the AC back to 160V !!

Seems you have to get every bit of it off to effect repair. Along the way
you will see corroded leads and PCB link wires - there is a 2.2kohm next
to the filter caps that is buried in the glue and needs replacing.

This is worse than the Yellow Glue problem as it becomes conductive in areas
that have no heat.

Could the black colouring be carbon ??


... Phil

[Gareth Magennis]

"Phil Allison" <phi...@tpg.com.au> wrote in message
news:bb6d6f...@mid.individual.net...

I've been seeing this black stuff for a while now, on KRK, Alesis and Tannoy
powered monitors, but curiously not other types of equipment.
Perhaps they are all made in the same factory.

Could well contain carbon.
http://www.specialchem4coatings.com/tc/color-handbook/?id=black

This stuff get it off quite nicely.
http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160

(Arfa Daly recommended this product a while ago on this forum, I've tried
it, and it does work well)



Cheers,

Gareth.

[Phil Allison]

"Gareth Magennis"
> "Phil Allison"

>
>> ** Hi to all,
>>
>> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>>
>> I have exactly the same problem, but the glue is now black instead -
>> with a KRK 'Rokit 5" powered monitor - from China of course. Both PCBs
>> are liberally covered in the stuff, more on the amplifier and PSU one.
>>
>> Symptoms in my example were loud crackling and low volume - which
>> recovered when I wound the AC back to 160V !!
>>
>> Seems you have to get every bit of it off to effect repair. Along the way
>> you will see corroded leads and PCB link wires - there is a 2.2kohm
>> next to the filter caps that is buried in the glue and needs replacing.
>>
>> This is worse than the Yellow Glue problem as it becomes conductive in
>> areas that have no heat.
>>
>> Could the black colouring be carbon ??
>>
>
>

> I've been seeing this black stuff for a while now, on KRK, Alesis and
> Tannoy powered monitors, but curiously not other types of equipment.
> Perhaps they are all made in the same factory.

** Very likely.

> Could well contain carbon.
> http://www.specialchem4coatings.com/tc/color-handbook/?id=black

** Wot a bad idea.

>
> This stuff get it off quite nicely.
> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>

** Does it simply dissolve the horrible stuff ?

What the KRKs use goes rock hard and has to be chipped of with *ridiculous*
amounts of force.

I have been using a jeweller's screwdriver, hit repeatedly with a back end
of a small shifting spanner.

Stone mason's stuff.



... Phil

[Gareth Magennis]

"Phil Allison" <phi...@tpg.com.au> wrote in message

news:bb7lgp...@mid.individual.net...

That sounds more like an epoxy, maybe not the same stuff?
But why would it need to be black anyway? Just makes it more expensive than
uncloloured adhesive.

The flux cleaner I think just softens it, so it doesn't adhere as strongly
to the PCB. Arfa might be able to confirm or deny this.



Incidentally, I recently made my own black speaker glue (for fixing dust
caps) using Evostick and laser printer toner. Works a treat, and a damn
sight cheaper than this tiny tube of what is probably the same stuff.

http://www.saveltd.co.uk/jbl-professional-moyen-rs-3087-speaker-driver-cement-glue-4125-p.asp




Gareth.

[Phil Allison]

"Gareth Magennis"
> "Phil Allison"

>>
>>> I've been seeing this black stuff for a while now, on KRK, Alesis and
>>> Tannoy powered monitors, but curiously not other types of equipment.
>>> Perhaps they are all made in the same factory.
>>
>> ** Very likely.
>
>>>

>>> This stuff get it off quite nicely.
>>> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>>>
>>
>> ** Does it simply dissolve the horrible stuff ?
>>
>> What the KRKs use goes rock hard and has to be chipped of with
>> *ridiculous* amounts of force.
>>
>> I have been using a jeweller's screwdriver, hit repeatedly with a back
>> end of a small shifting spanner.
>>
>> Stone mason's stuff.
>>
>

> That sounds more like an epoxy, maybe not the same stuff?

** It's the same horrible stuff - just black.

Time and a bit of heat turns it into rock.

> But why would it need to be black anyway?

** IEC inlets, rocker switches, XLRs and metal back panels are commonly
black.

So it matches, when used to achieve an air seal around them, like in this
case.



... Phil

[N_Cook]

So that makes it 3 different types that cause such problems.
The yellow glue stuff
The white softish conformal coating material that breaks down leaving a
distinctive oily film, plus corrossion/conduction problems
This black stuff now
Does no manufacturer do accelerated aging of these sorts of materials
before selling them

[Gareth Magennis]

> Could well contain carbon.
> http://www.specialchem4coatings.com/tc/color-handbook/?id=black
>

From that site:

Flocculation
Following dispersion small particles of carbon black have a tendency to
flocculate. To minimize this tendency it is necessary to take utmost care
when diluting paints. Only small calculated additions should be made with
thorough homogenization between additions



So it could be that over time, whatever is used as a pigment "flocculates"
and forms solid flakes or a layer of conductivity on the PCB.

(Being as the pigment particles are not dissolved in a medium as a solution,
but are merely mixed with it)



Gareth.

[dave]

http://www.krksys.com/krk-history.html

[Jeff Liebermann]

Ouch. That could be serious. If the conductive carbon particles
remain suspended in solution, the goo will not be conductive because
the space between the particles is filled with the non-conductive base
glue. However, if the carbon particles are heavier than the glue,
they might precipitate out of the colloidal solution, and settle to
the bottom of the glue joint. The carbon particles might then overlap
each other, producing a conductive layer. If the carbon particles are
lighter than the glue, they could float to the surface and form a
conductive layer on the surface. Much depends on how the goo was
mixed and applied. If it hardens quickly, I don't think there will be
a problem. If it hardens very slowly, expect trouble. If it was
diluted with solvent, it probably produce conductive clumps of carbon.


--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Gareth Magennis]

"Jeff Liebermann" wrote in message
news:2sqt491eg4a66sv7c...@4ax.com...

There may be other factors involved.
This adhesive is typically found in powered speakers, which can undergo
quite large temperature change cycles. This could regularly soften the
glue, which might in turn cause cyclic migration or clumping of any free
conductive particles therein.

But I'm not an adhesive expert, this is all just an interesting guess.



Gareth.

[Arfa Daily]

>> This stuff get it off quite nicely.
>> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>>
>
> ** Does it simply dissolve the horrible stuff ?

No. It 'softens' it which then makes it become sort of 'plastic' so that it
can be peeled off the board without taking all the little surface mount
components with it

>
> What the KRKs use goes rock hard and has to be chipped of with
> *ridiculous* amounts of force.
>
> I have been using a jeweller's screwdriver, hit repeatedly with a back end
> of a small shifting spanner.

This is the sort of thing that I was doing before, but one day I got so fed
up of having to use such force that I started trying all the liquid
chemicals that I had, just in case. The Servisol 160 is my defluxer of
choice, and I have used it for many years. I sprayed some on the glue, and
left it for 5 minutes, and when I tried again to shift the stuff, it had
ceased being hard and I was able to peel it with a blunt scalpel. Make no
mistake, it still doesn't come off easily, but much easier than when it is
hard before treatment. Whether it would have the same effect on your black
stuff, though ... ??

Arfa

[Phil Allison]

"Arfa Daily"

** Servisol 160 is mixture of a few solvents including "naphtha" the magic
ingredient in WD-40.

http://www.crcind.com/wwwcrc/msds/UK20046-23.htm

It is also highly flammable and toxic - so it must do the job ....



... Phil

[Phil Allison]

"dave"

> http://www.krksys.com/krk-history.html


** Ok, Dave, I do see the link.

Is there a particular reason you posted that to me right now ?

Juts what do you think you are doing - Dave ??




... Phil

[dave]

Pointing out that KRK was a good company until Gibson bought them. Their
original monitors are quite good. In fact, they turned my head at the
AES convention where they were debuted.

[William Sommerwerck]

"Phil Allison" wrote in message news:bbab1i...@mid.individual.net...

> Just what do you think you are doing -- Dave ??

"I can feel my mind going, Dave. Thee is no question about it."

[Gareth Magennis]

"William Sommerwerck" wrote in message news:l2p1q0$kq9$1...@dont-email.me...

"Phil Allison" wrote in message news:bbab1i...@mid.individual.net...

> Just what do you think you are doing -- Dave ??

"I can feel my mind going, Dave. Thee is no question about it."

http://www.youtube.com/watch?v=41U78QP8nBk

[N_Cook]

Does your Servisol 160 say what its primary solvent constituent is ,
other than uninformitive "hydrocarbon solvent" ?

[Arfa Daily]

"N_Cook" <div...@tcp.co.uk> wrote in message
news:l2tn2u$dcm$1...@dont-email.me...

See the link that Phil gave ...

http://www.crcind.com/wwwcrc/msds/UK20046-23.htm

Arfa

[N_Cook]

The main ingredients of
Electrolube Lead Free Flux Remover, different pricipal ingredient
CYCLOHEXANE 30-60%
PROPAN-2-OL 10-30%
1-METHOXY-2-PROPANOL 10-30%

Any chemists here?
So were you getting softening just by using petroleum as a solvent?

[Jeff Layman]

On 07/10/2013 15:52, N_Cook wrote:
>>>
>>> Does your Servisol 160 say what its primary solvent constituent is ,
>>> other than uninformitive "hydrocarbon solvent" ?
>>>
>>
>> See the link that Phil gave ...
>>
>> http://www.crcind.com/wwwcrc/msds/UK20046-23.htm
>>
>> Arfa
>
>
> The main ingredients of
> Electrolube Lead Free Flux Remover, different pricipal ingredient
> CYCLOHEXANE 30-60%
> PROPAN-2-OL 10-30%
> 1-METHOXY-2-PROPANOL 10-30%
>
> Any chemists here?
> So were you getting softening just by using petroleum as a solvent?

All the constituents are organic solvents. 1-methoxy-2-propanol is a
particularly good solvent used in paints and other materials. For
example, see here:
http://www.recochem.com.au/index.php/products/industrial_products/solvents_penetrants_general/item/methoxy_propanol

--

Jeff